Preparation of long-lasting action injection formulation comprising avermectins with dimethicone as medium was described in Chinese Patent Applications Nos. CN03138019.0 and CN03156876.9. Preparation of long-lasting action veterinary formulation comprising N-phenyl pyrozle agents against parasites (e.g. fipronil) with dimethicone as medium was described in Chinese Patent Application No. CN03148883.8. In addition, preparation of long-lasting action formulation comprising NSAIDs was described in Chinese Patent Application No. CN03153569.0. Furthermore, our recent research suggested that formulation comprising triazine anticoccidial drugs, halofuginone anticoccidial drugs, imidacloprid, diflubenzuron, ceftiofur or sex hormone agents, which is prepared with dimethicone as medium, is stable and easy for injection and can provide satisfactory sustained action and cause little tissue damages. At the same time, it is stable and injectable. Therefore, the present invention includes the subject matters disclosed in our prior Chinese Patent Application Nos. CN03138019.0, CN03156876.9, CN03148883.8 and CN03153569.0, and also includes dimethicone-based preparation of long-lasting action injection formulation used for drugs such as anticoccidial drugs, sex hormone agents, imidacloprid, etc.
Dimethicone, also known as silicone oil, consists of a series of dimethylsiloxane polymers with various viscosities (see Zheng Junmin, Polymer Science for Pharmaceuticals, China Medical and Pharmaceutical Technology Press, August 2000, 1 Edition, pp 169-170). It is an oily liquid, highly hydrophobic and physiologically inert. Its viscosity changes little within the application temperature range (from −40° C. to 50° C.). Dimethicone is highly resistant to oxidation and can withstand sterilization at 150° C. for an hour. It is non-reactive to most compounds and very stable when mixed with any chemicals and drugs described in the present invention. The drugs and suspension agents (e.g. hydrogenated castor oil) described in the present invention are substantially insoluble and do not swell in dimethicone. These features are an important basis for dimethicone to be used to prepare the injection formulation of the present invention.
The experiments performed in the present invention suggested that: (1) subcutaneous injection of dimethicone at a dose between 4 ml to 6 ml per injection site per time to subjects (e.g. bovine and caprine) caused no side effect such as obvious tissue damage, swelling, agglomeration, granuloma, etc. Thus, from the view point of bio-compatibility, dimethicone is suitable to be used as medium to prepare formulation for subcutaneous injection. (2) Therapeutic drugs, for example avermectins, N-Phenyl pyrazoles against parasites, triazine anticoccidial drugs, imidacloprid, diflubenzuron, sex hormones, NSAIDs and ceftiofur, penicillin G potassium salt or penicillin G sodium salt, are almost insoluble in dimethicone (solubility less than 0.01%). Therefore, this will not pose any stability problem when using silicone as medium to prepare suspensions comprising the aforesaid drugs, which is one of the important factors usually affecting the sustained action of a long-lasting formulation. (3) Hydrogenated castor oil does not dissolve or swell in silicone oil, and therefore the combination of silicone oil and hydrogenated castor oil can be used as medium to prepare liquid suspensions. When hydrogenated castor oil used within the proper range (0.2% to 0.5%), the resulting liquid suspension is better in terms of stability, fluidibility, injectability and long-lasting releasing effect than the injection formulation prepared using water, vegetable oil or other organic liquid as the suspension medium. Hydrogenated castor oil functions as a suspending agent and enhances the effect of sustained releasing. In addition, when the formulation of the present invention is prepared by the micro powder crystallizing method, the presence of hydrogenated castor oil suppresses the growth of the crystal nucleus of active ingredients, whereby producing micro powder of active ingredients with a particle size of 20 micrometers or smaller. (4) By mixing the active ingredients with hydrogenated castor oil or with the-combination of hydrogenated castor oil and ethylcellulose to produce solid dispersion micro powder with particle size smaller than 300 micrometers, then dispersing the micro powder in silicone oil and grinding with a colloid mill or a ball mill, a long lasting release formulation containing solid dispersion of various particle sizes (from 10 micrometer to 150 micrometers) can be produced. Further, the sustained releasing effect of the formulation may be modified by adjusting the particle size of the solid dispersion and the proportion of hydrogenated castor oil relative to the active ingredients. For instance, sustained release formulations with various durations of effectiveness may be prepared as follows: mixing avermectins with hydrogenated castor oil to produce two solid dispersions with the avermectins to hydrogenated castor oil equal to 1:2 and 2:1, respectively, then mixing the two solid dispersions at a given ratio and dispersing the mixture in silicone oil, and producing the solid dispersion in the system with the particle size varying between 85 micrometers to 120 micrometers by controlling the extent of grinding. The formulation can provide an effective sustained releasing period up to 140 days following a single administration. Furthermore, the injection prepared by the above method has better injectability, stability and biocompatibility than water or vegetable oil based sustained release formulations for solid dispersion micro powder of avermectins/hydrogenated castor oil. Specifically, the formulation using water as medium has three disadvantages. First, it has difficulty to maintain an effective sustained releasing for more than 80 days. Second, it has poor injectability and, without adding more water soluble suspension assisting agents, solid suspension phase may “separate” from the water phase, causing injection failure due to blocking of the syringe needle. Third, it results in tissue lumps around the injection site. Other organic liquid based long-lasting formulations have similar problems. Therefore, all previous long-lasting injection formation have proved to have little or no commercial value.
Avermectins suitable for practicing the present invention include, but not limited to, abamectin, ivermectin, emamectin, eprinomectin, doramectin, moxidectin, 4″-O-carbamylmethyl-abamectin B1 and other avermectin derivatives. The avermectins and avermectin derivatives were described in detail in Chinese Patent Application CN 1345327A (WO00/58328). Structurally, avermectins bear the common structure of macrolide and for this reason they are also called macrolides. The avermectins are highly effective in ridding of or killing those parasites widespread among animals, for example, internal parasites such as nematodes and external parasites such as mite, tick, louse and maggot. Administration of currently available commercial drugs at a dose of 0.2 mg to 0.4 mg/kg bodyweight can repel more than 95% of the parasites, and the action can continue 10 to 20 days. High effectiveness is an important biological basis for the avermectins to be prepared in long-lasting action formulations.
Avermectins are highly hydrophobic and hardly dissolvable in silicone oil, which is an important chemical basis for the avermectins to be prepared in long-lasting action formulations.
However, avermectins do not have the ability to kill parasite eggs. The life cycle for parasites like itch mite, vampire louse, etc. growing from eggs to adults is about 20 days. Therefore, in order to prevent and treat the problems caused by the parasites, two or more administrations of the drug are needed when using in conventional injection or oral formulations. In addition, the parasites like nematodes are widespread in the environment and have the opportunity to infect animals repeatedly. Sustained releasing formulation can prevent animals from be infected by those parasites for a long period with a single administration. Therefore, the situation has created a need for developing long-lasting action or sustained releasing formulations for avermectins.
According to the present invention, avermectins may present in the formulation in the form of fine particles (smaller than 100 micrometers) or in the form of carrier particles. The carrier particles refer to solid dispersion particles, micro-balls, microcapsules, liposome in the solid state, or nano-particles, which are made of avermectins and carrier material for sustained release. The carrier material for sustained release may be hydrogenated castor oil, ethylcellulose, polyesters, polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP), etc., which may be used alone or in combination. For example, to practice the present invention the carrier material for forming solid dispersion with avermectins may be selected from of the following: hydrogenated castor oil, the combination of hydrogenated castor oil and ethylcellulose, the combination of hydrogenated castor oil, ethylcellulose and polyvinyl pyrrolidone, the combination of ethylcellulose and polyvinyl pyrrolidone, the combination of hydrogenated castor oil and polyvinyl pyrrolidone, the combination of ethylcellulose and polyethylene glycol, the combination of hydrogenated castor oil and polyethylene glycol, or the combination of ethylcellulose and polyethylene glycol. The fast release action or sustained release action of the formulation may be controlled by adjusting the ratio between water-soluble carrier (e.g. PVP and PEG) and hydrophobic carrier (e.g. hydrogenated castor oil and ethylcellulose). The carrier material for sustained release used in the present invention should not dissolve or swell in dimethicone, which is an important basis to ensure the carrier particles' stability and the sustained releasing effect of the formulation.
Experiments suggested that avermectins ground by the air-blow method is difficult to achieve desired particle size. Additionally, this grinding method is energy-consuming, prone to dust contamination and difficult to maintain sterilized processing. Thus, for the present invention it is preferred that the micro powder crystallization method be used to produce fine power of avermectins. The following further details this method: through heating, dissolving and melting avermectins and hydrogenated castor oil in organic solvent with a low boiling point, such as, for example, ethanol, acetic ether and methylene trichloride and then, upon cooling of the solution, adding dimethicone with stirring so that avermectins will precipitate in micro crystal form. Or, alternatively, dispersing avermectins in a small amount of dimethicone to make a viscous liquid, grinding in wet condition (e.g. grinding with a ball mill or a colloid mill), and adding more medium (dimethicone) to the final volume. In addition, it can be made by a method comprising the following steps: producing solid dispersion with avermectins and carrier material (e.g. hydrogenated castor oil), grinding the solid dispersion to micro powder, and dispersing the powder in dimethicone to obtain an injection preparation of the present invention.
The long-lasting action formulation of the present invention, when administered at the dose of 1 to 3 mg of abamectin agents per kilogram of bodyweight, can maintain the drug effectiveness up to 60 to 120 days or longer after a single administration. The effective duration can be modified by adjusting the dosage.
The N-Phenyl pyrazole agents used in the present invention, for example, fipronil, are highly active synthetic chemical insecticides. They have been widely used in agriculture for killing noxious insects. They are also used in the prevention and treatment of problems caused by external parasites, especially fleas and ticks. The preparation methods, formulations and application of fipronil, were described in detail in Chinese Patent CN1018733B. The commercial products of fipronil, such as those in casting formulation and spray, are mainly used to repel and kill flea on cats and dogs and boophilus on cattle. According to the present invention, the sustained release formulation of fipronil was prepared with dimethicone and hydrogenated castor oil as the medium, for repelling and killing flea and boophilus. Subcutaneous injection of this formulation, the effect may be maintained for 3 to 6 months or longer following a single administration.
The Nonsteroidal Anti-inflammatory Drugs (abbreviated as NSAIDs) used in the present invention have the effects of fever reducing, pain relieving and anti-inflammatory, as has been described in detail in some of the pharmaceutical books and manuals (e.g. Ni Wenji, Li Anliang, Pharmaceutical Chemistry, Higher Education Press, 1999, pp 348-375). NSAIDs include the antipyreitc and analgesics category and anti-inflammatory category. The latter includes, for example, salicylates, pyrazolones, aryl alkanoic acids, fenamic acids, benzothiazines etc. NSAIDs' effect is based on inhibition of the prostaglandin synthesis via the cyclooxygenase enzymes (COX). Therefore, other water insoluble COX-2 inhibitors are contemplated in the present invention as well. Water insoluble and slightly water soluble NSAIDs as well as NSAIDs that can be converted to water insoluble through chemical modification are suitable to application of the present invention. The Preferred NSAIDs for practicing the present invention includes indomethacin, ketoprofen, flunixin, diclofenac and piroxican etc. The sustained release formulation of NSAIDs is prepared with silicone oil and hydrogenated castor oil as the carrier material for sustained release. The formulation prepared accordingly is stable, bio-compatible, injectable and with good sustained release effect. It is suitable for subcutaneous injection to animals.
5. The compound Imidacloprid used in the present invention has been widely used in the prevention and treatment of problems caused by noxious insects in agriculture. In the veterinary field, they are mainly used for external parasites on cats and dogs. The existing commercial products are of casting formulation and, when administered through skin at the dose of 10 mg/kg body weight, can maintain effectiveness up to about 1 month after a single administration. In contrast, in the sustained release formulation of the present invention, when administered by subcutaneous injection at the dose of 10-100 mg/kg body weight, it can maintain effectiveness up to 80 to 360 days after a single administration. The compound diflubenzuron used in the present invention is a benzy phenylthiourea insecticide and can inhibit the synthesis of chitin in insects, making the larva unable to form new epidermis, which leads to death. Diflubenzuron had been widely used in agriculture in dealing with noxious insects. Outside China, it has been prepared in liquid formulation used in bathwater for getting rid of or killing lice infecting the sheep. In the present invention, diflubenzuron is prepared in a dimethicone based injection formuation for repelling and killing external parasites, such as, louse and flea. It can provide long-lasting action up to 2 to 4 months. The present invention also suitable for the following compounds: triflumuron, cyromazine, estrogen, progesterone, androgen, triazine anticoccidial drugs (e.g. toltrazuril and dliclazuril), cephalosporins (e.g. ceftiofur hydrochloride, ceftiofur sodium and ceftiofur free acid) and other antibiotics. Those compounds are known and commercially available. According to the present invention, they may be prepared in the sustained release formulation with silicone oil, silicone oil/hydrogenated castor oil or silicone oil/hydrogenated castor oil/ethylcellulose.